Moisture problems in buildings have received an increasing amount of interest as durability and mold issues have come to the attention of the public. Mold problems in buildings generally develop when certain conditions are present. These conditions comprise the presence of a food source, mold spores, water, and a temperature conducive to mold growth. Of these conditions, moisture is generally regarded as the one that is the most likely to be susceptible to control, in that most building materials provide a food source, mold is ubiquitous in the environment, and typical temperatures in buildings are conducive to growth of a wide range of molds. Other durability problems such as rotting of structural members of a building can also be caused by excess moisture in building components. Moisture-related issues have escalated to the point where significant litigation is occurring, and homeowners, builders, and insurance companies are all being adversely affected.
As moisture issues in buildings continue to draw significant attention, tools for diagnosing excess moisture within the building envelope are needed by practitioners and researchers. Ideally, such a tool would be non-destructive, and in this regard, the anecdotal evidence seems to indicate that one of the most common methods used to locate moisture problems involves simply tearing walls apart. However, better alternatives are available and should obviously be used in place of these more primitive techniques.
Considering some of these alternatives, instruments such as electrical resistance pin probes, capacitance meters, and relative humidity sensors are frequently used to estimate the moisture content of building materials. Each of these instruments has positive and negative features as described by several authors. (See, e.g., TenWolde. A, and G. E. Courville, 1985, “Instrumentation for Measuring Moisture in Building Envelopes,” ASHRAE Trans. Vol. 91, pp. 1101–1115; Healy, W. M., 2003, Moisture Sensor Technology—a summary of techniques for measuring moisture levels in building envelopes. (to appear in ASHRAE Trans.); Derome, D., A. Teasdale-St-Hilaire, and P. Fazio., 2001. Methods for Assessment of Moisture Content of Envelope Assemblies. Thermal Performance of the Exterior Envelopes of Buildings VII. Conference Proceedings, Clearwater Beach, Fla. Dec. 2–7, 2001, ASHRAE. ) The use of pin probes is a popular technique for detecting moisture in buildings is by using pin probes. Two pins are inserted into the building material, and the electrical resistance between the probes is measured. However, this technique is destructive, and gaining access to layers within the wall can be difficult. Another drawback of probes such as a pin probe is the fact that contact is needed with the moist specimen in order to diagnose excess moisture. Tools that do not require contact to locate moisture problems in walls would be preferable in finding problems in a non-destructive manner. Furthermore, techniques that can scan larger areas of the building envelope would enable isolating areas of excessive moisture in a manner that is substantially more efficient than the more laborious approaches of the prior art that involve examining individual areas with localized meters and sensors.
One prior art technique, the capacitance meter, involves pressing pads against a wall and measuring the capacitance of the wall. However, this technique is not able to pinpoint the location of water within the wall. More specifically, while a capacitance meter might indicate the presence of water in a wall, such a meter cannot provide very precise spatial resolution with respect to the location of the water.